JPH0374873B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an interference wave removal receiving device that removes mixed interference waves and receives residual sideband modulation television broadcast waves, and in particular, With a configuration that is simple enough to be easily added to a receiver, a plurality of interference waves can be removed without deteriorating the received image quality.

(Prior art) Conventionally, in order to remove interference waves mixed in received residual sideband modulation television broadcast waves,
A band rejection filter with a narrow bandwidth, ie, a so-called notch filter, is inserted into the intermediate frequency of the receiver in order to remove only the mixed interference wave component as much as possible. However, with such conventional interference wave removal means, when the frequency of the interference wave is close to the video carrier frequency, especially when the frequency of the interference wave is close to the video carrier frequency, If the interference waves are mixed in, the interfering waves can be removed by inserting a notch filter, and even if the beat component between the disturbing interference waves and the video carrier wave has been removed, the notch filter will remove the video signal near the interfering wave frequency. Since components are also lost at the same time, there is a drawback that it is difficult to sufficiently improve the quality of the received image.

Another method is to synthesize the received waves from two or more receiving antennas placed close to each other by relatively adjusting the amplitude and phase. Conventionally, interference waves were removed by aligning the null direction with the arrival direction of the interference wave, but if the interference wave is a reflected wave via the ionospheric sporadic E layer, depending on the propagation conditions, If the arrival direction of the interference waves changes due to a change, the null direction must be readjusted each time, and in particular, there is a drawback that it is extremely difficult to eliminate a plurality of interference waves.

(Objective) The object of the present invention is to eliminate the above-mentioned conventional drawbacks, and eliminate interference waves that mix into the double-sideband transmission band of received vestigial sideband modulation type television broadcast waves and cause significant reception interference. To provide an interference removal receiving device capable of stably and reliably removing even when a plurality of interference waves are mixed in, without impairing original received image quality, with a relatively simple circuit configuration. It is in.

Another object of the present invention is to provide the above-mentioned type of circuit by adding a circuit having a simple configuration according to the present invention to an intermediate frequency stage of a conventional television receiver such as a television relay broadcast receiving equipment or a home receiver. It is an object of the present invention to provide an interference wave removal receiving device that can easily remove mixed interference waves.

(Summary of the Invention) In other words, the interference wave removal receiving device of the present invention uses a signal transmitted in both sidebands as a quadrature phase component of a demodulated signal of a carrier signal component of a modulated wave such as a vestigial sideband modulation type television broadcast wave. component does not appear, only the signal component that is transmitted in a single sideband, and interference waves also appear among them.The interference wave extracted by skillfully taking advantage of this fact is mixed into the carrier signal component of the received modulated wave. This system is designed to cancel out the interfering interference waves and sufficiently remove only the mixed interference waves. carrier regeneration means for regenerating; carrier phase shifting means for shifting the phase of the carrier wave component regenerated by the means by π/2; synchronous detection means for synchronously detecting a carrier signal component of a modulated wave to extract a quadrature phase component; a modulation means for modulating the reproduced carrier wave component phase-shifted by π/2 by the quadrature phase component; at least one frequency component that is the same as the interference wave identified from the carrier signal component of the received modulated wave by extracting the same frequency component as the interference wave.
and subtraction means for subtracting the extracted same frequency component from the carrier signal component of the received modulated wave to cancel out and remove the interference wave mixed into the double sideband transmission component. It is characterized by this.

(Example) The present invention will be described in detail below with reference to the drawings.

First, in order to facilitate understanding of the present invention, the sideband distribution characteristics, in-phase component distribution characteristics, and quadrature component distribution characteristics of vestigial sideband modulation television broadcast waves are shown in FIGS. 1a, b, and c. are shown respectively. That is, the sideband distribution of the television broadcast wave shown in FIG. 2A is divided into an in-phase component shown in FIG.

Now, when the video signal in the television broadcast wave is G(t) and the video carrier angular frequency is ω _p , the amplitude modulated wave G(t) _cps ω _p t produced by the amplitude modulated television broadcast wave is shown in Fig. 1. When the vestigial sideband is transmitted using the sideband distribution characteristic as shown in a, the amplitude modulated wave is expressed by the following equation (1).

C(t) _cps (ω _p t+θ _p ) −S(t) _sio (ω _p t+θ _p ) (1) Here, θ _p is the phase at the image carrier angular frequency ω _p , and C(t) and S(t) is a video signal G applied to a circuit having a transfer function when the video carrier angular frequency ω _p is shifted to 0 for each distribution characteristic of the in-phase component and the quadrature component shown in FIGS. 1b and 1c, respectively. These are the output responses obtained when adding (t).

Therefore, when the amplitude modulated wave expressed by equation (1) is synchronously detected using a carrier wave having a relative phase expressed by the following equation (2), an in-phase component C(t) is obtained.

cos (ω _p t + θ _p ) (2) On the other hand, the carrier wave expressed by this equation (2) is obtained by delaying the carrier wave by π/2, and the phase is different by π/2 according to the following equation (3). When the amplitude modulated wave of equation (1) is synchronously detected using a carrier wave with a relative phase expressed as , a quadrature phase component S(t) is obtained.

sin (ω _p t + θ _p ) (3) In this case, as mentioned above, the vestigial sideband modulation method television broadcast wave is transmitted in both sidebands.
In the angular frequency region of μ, only the quadrature phase component S(t), which does not include the video signal component, is obtained. However,
As shown in Figures 1a to 1c, within the double sideband transmission band corresponding to the angular frequency range 0 to μ mentioned above, the following
Suppose that an interference wave with an angular frequency ω _p +δ expressed by equation (4) is mixed.

Acos {(ω _p + δ)t + (θ _p +φ〓)} (4) Here, (θ _p +φ〓) is the relative phase of the disturbance wave,
A is the absolute value of its amplitude.

This interference wave in equation (4) can be detected using equations (2) and (3), which are the same as those obtained by synchronously detecting the amplitude modulated waves as described above.
When similarly synchronously detecting the carrier waves expressed by the following equations, the in-phase component expressed by the following equation (5) and the quadrature phase component expressed by the following equation (6) are obtained as the synchronous detection output. You can get each.

A/2cos(δt+φ〓)+1/2C(t) (5) −A/2sin(δt+φ〓)−1/2S(t)(6
) Out of the synchronous detection output of such interference waves, the quadrature component of equation (6) is guided to a bandpass filter or low-pass filter having a band value μ, and the above-mentioned (6)
The component of the first term of the equation, that is, the quadrature phase component of the interference wave expressed by the following equation (7) is extracted.

−A/2sin(δt+φ〓) (7) Multiplying the quadrature phase component of the disturbance wave in equation (7) by the quadrature phase carrier wave in equation (3), the quadrature phase of the disturbance wave expressed by the following equation (8) is obtained. An amplitude modulated wave with different components is obtained.

A/4cos {(ω _p +δ)t+(θ _p +φ〓)} A/4cos{(ω _p −δ)t+(θ _p −φ〓)}(8) According to the first term of this equation (8), If we separate and extract the interference wave component with the angular frequency ω _p +δ expressed by using a bandpass filter or high-pass filter and multiply its amplitude by 4, we can obtain exactly the same interference as the mixed interference wave expressed by equation (4). The wave component will be obtained.

Therefore, the interference wave of equation (4) mixed in the double-sideband transmission band can be canceled out and removed by adding the interference wave component of the first term of equation (8) in antiphase. At this time, the video signal component is not changed in any way, and as a result, the original amplitude modulated television broadcast wave from which only the interfering interference waves are almost completely removed is obtained.

In the above, it is assumed that the interference wave is mixed in the upper sideband part of the both sideband transmission band of the amplitude modulated television broadcast wave, and that the interference wave is expressed by equation (4). When a wave enters the lower sideband portion of the doublesideband transmission band, the following procedure is performed.

That is, the interference wave in this case is expressed by equation (9).

Bcos {(ω _p −δ)t+(θ _p +φ〓)} (9) Here, (θ _p +φ〓) is the relative phase of the interference wave,
B is the absolute value of its amplitude.

When the interference wave expressed by equation (9) is synchronously detected using the carrier wave expressed by equation (3), a quadrature phase component expressed by the following equation (10) is obtained as a synchronous detection output.

B/2sin(δt−φ〓)−1/2S(t)(10) This quadrature component is guided to a bandpass filter or lowpass filter with a bandwidth μ(10)
The component of the first term of the equation, that is, the interference wave quadrature component expressed by the following equation (11) is extracted.

B/2sin(δt−φ〓) (11) Multiplying the quadrature phase component of the disturbance in equation (11) by the quadrature carrier in equation (3), the quadrature phase of the disturbance wave expressed by the following equation (12) is obtained. An amplitude modulated wave by the component is obtained.

B/4cos {(ω _p −δ)t+(θ _p +φ〓)} −B/4cos{(ω _p +δ)t+(θ _p −φ〓)}
(12) Separate and extract the interference wave component of the angular frequency ω _p −δ expressed by the first term of equation (12) using a band pass filter or a low pass filter,
If the amplitude is quadrupled, a disturbance wave component that is exactly the same as the mixed interference wave expressed by equation (9) will be obtained, and the interference will occur in exactly the same way as when the interference wave mixes in the upper sideband. It is possible to cancel and remove wave components.

FIG. 2 shows an example of the basic structure of the interference wave cancellation receiving apparatus of the present invention which cancels and eliminates mixed interference waves based on the above-mentioned operating principle. In the illustrated configuration example, a vestigial sideband modulation type television broadcast wave mixed with interference waves in the manner described above is received,
The intermediate frequency (IF) signal obtained by frequency conversion is guided from the input terminal to the carrier wave regeneration circuit 1, a carrier wave component in phase with the video carrier wave from the carrier signal component is regenerated, and the regenerated carrier wave component is shifted by π/2. Phase delay circuit 2
to form a carrier wave component having a phase quadrature with respect to the image carrier wave described above. Next, the quadrature phase carrier wave component is supplied to the multiplier 8, where it is multiplied by the IF signal led from the input terminal and subjected to synchronous detection. π/ The quadrature phase carrier component from the two-phase shift/delay circuit 2 is also supplied to the multiplier 5, and these components are multiplied together to perform amplitude modulation, thereby generating the quadrature phase component of the interference wave from equations (8) to (12). Accurately reproduces amplitude modulated waves. The multiplication output from the multiplier 5 is guided to bandpass filters 7 and 8 so that upper and lower sideband components in the double-sideband transmission band can be extracted, respectively. The wave outputs of the bandpass filters 7 and 8 are guided to the switching device 12, and depending on the result of identifying which of the upper and lower sidebands the interference wave is mixed in as will be described later, the wave output of either one is changed. After adjusting the level using the level adjustment circuit 9, the signal is sent to the subtraction circuit 11, and is subtracted from the IF signal supplied from the input terminal via the delay circuit 10 to compensate for the delay time caused by the above signal processing. For example, the original IF signal obtained by canceling and removing only the mixed interference waves from the IF signal is taken out from the output terminal.

Therefore, in the interference wave removal receiver of the present invention having the configuration shown in FIG. According to the result of identifying the mixed band of
By selectively using , you can ensure easy removal. Also, the number of mixed interference waves is 1
It may be multiple waves instead of one wave.

In the above explanation, an example of the configuration of the interference wave removal receiving device of the present invention is used when single or multiple interference waves are mixed in either the upper or lower sideband of the double-sideband transmission band of the television broadcast wave. However, in the case where single or multiple interference waves are mixed simultaneously in both the upper and lower sidebands, the present invention is designed to cancel and remove the interference waves in the upper and lower sidebands in the same manner as described above. An example of the configuration of the receiving device is shown in FIG.

Now, the interference waves mixed in the upper and lower sidebands of the television broadcast waves are expressed as follows (13).
and (14).

Acos {(ω _p + δ _u )t+(θ _p +φ〓 _u )} (13) Bcos {(ω _p −δ _l )t+(θ _p +φ〓 _l )} (14) Therefore, the configuration example shown in the third figure As is clear from a comparison with the configuration example shown in the second figure, in the configuration example shown in the second figure, the bandpass filters 7 and 8 and the switch 12 separate the upper sideband component from the multiplication output of the multiplier 5. The circuit portion for selectively switching and extracting the lower sideband components includes n bandpass filters 13-1 to 13-n each having a pass band corresponding to a plurality of frequency bands obtained by dividing the doublesideband transmission band. The wave outputs of the filters 13-1 to 13-n are replaced with n open/close switches SW ₁ to SW _o that can be selectively taken out by opening and closing the wave outputs, and if necessary, the wave outputs of the filters 13-1 to 13-n can be selectively extracted.
It is possible to relatively eliminate each of the mixed interference waves.

Therefore, the IF signal mixed with the interference waves expressed by equations (13) and (14) at the same time can be expressed as (3)
The quadrature carrier wave multiplier 3 is expressed by
When synchronously detected by supplying to
The quadrature phase component of the interference wave expressed by the following equation (15) is obtained at the output of .

−A/2sin(δ _u t+φ〓 _u ) +B/2sin(δ _l t−φ〓 _l ) (15) Next, the output of the low-pass filter 4 expressed by this equation (15) and the output of the low-pass filter 4 expressed by equation (3) are The output E _i of the multiplier 5 performs multiplication with the quadrature carrier wave represented by
For mixed disturbance waves in the upper sideband and lower sideband according to equations (13) and (14), the following equation (16) is obtained.
It can be expressed by the formula.

E _i =-A/2sin(δ _u t+φ〓 _u )・sin(ω _p t+θ _p
+B/2sin(δ _l t−φ〓 _l )・sin(ω _p t+θ _p ) =A/4cos {(ω _p +δ _u )t+(θ _p +φ〓 _u )}
−A/4cos {(ω _p −δ _u )t+(θ _p −φ〓 _u )} −B/4cos {(ω _p +δ _l )t+(θ _p −φ〓 _l )
}+B/4 cos {(ω _p −δ _l )t+(θ _p +φ〓 _l )}(1
6) The first and second terms on the right-most side of equation (16)
term, the third term, and the fourth term respectively as A _u , A _l , B _u ,
When expressed as B _l , the spectral distribution of each of these components is as shown in FIG.

Therefore, the interference wave components included in the delayed output IF signal of the delay circuit 10 in the configuration example shown in _{FIG .} Therefore, if each of these spectral components is extracted using the bandpass filters 13-1 to 13-n and then selectively extracted by the on/off switches _SW1 to _SW0 , the delay is reduced by canceling the subtraction circuit 11. A plurality of interference waves mixed into the output IF signal at the same time can be canceled out and removed at once in the same manner as in the configuration example shown in the second figure. Therefore, in the receiver of the present invention, the output of the multiplier that performs amplitude modulation is guided to a plurality of bandpass filters each having a pass band that is almost the same as the band of each interference wave and whose center frequency is different sequentially. Single or multiple mixed interference waves mixed in each sideband can be canceled out and removed at the same time.

In addition, as for the bandpass filter used in the above, if the interfering wave is a foreign FM broadcast wave via Sporadics E layer, the FM broadcast waves are arranged every 100KHz, so the center frequency should be set to
It is preferable to use a bandpass filter having characteristics similar to those used in a normal FM broadcast wave receiver with an interval of 100KHz.

Opening/closing switch SW ₁ in the configuration shown in the third diagram
SW _o depends on the number and frequency of mixed interference waves,
The wave output of one of the bandpass filters 13-1 to 13-n is selected to be used, and the on/off switches SW ₁ to SW _o are controlled by a switching signal having the configuration shown in FIG. 5, for example. This can be done automatically using a generator. In the switching signal generator having the configuration shown in the figure, when the interference wave is an angle modulated wave, such as interference of foreign FM radio waves by the Sporadic E layer, for example,
Taking advantage of the fact that television broadcast waves are amplitude modulated waves, the input IF is adjusted while sweeping the local oscillation frequency.
By converting the frequency of the signal, each frequency component within the IF signal band is sequentially converted to a constant frequency like a spectrum analyzer to demodulate the angle modulated wave, and the interfering interference angle modulated wave components are sequentially detected and each The frequency and number of mixed particles are identified, the identification result is taken out as a switching signal, and the open/close switch is controlled based on the switching signal.

That is, the input IF signal is guided to the multiplier 16,
Frequency conversion is performed by multiplying the swept local oscillation output supplied from the voltage controlled oscillator 15, and the converted output is passed through a narrowband bandpass filter 17 and a limiter 18.
The angle modulated wave is supplied to the FM detection circuit 19 via the FM detection circuit 19 to demodulate the angle modulated wave, and the detection output is converted into a DC voltage by the rectification circuit 20. Therefore, an output DC voltage is obtained from the rectifier circuit 20 each time the mixed interfering angle modulated wave is detected. Its output DC voltage is A-
The data is converted into digital data by a D converter 21 and sent to a processing unit (CPU) 22, where it is passed through a bandpass filter 13 corresponding to the frequency of the mixed interference wave.
A switching signal is generated to control the on/off switches SW ₁ to SW _o so as to extract any one of wave outputs from -1 to 13-n. Note that, referring to the state of mixed interference wave detection, the CPU 22 sends out a digital sweep signal to sweep the oscillation frequency of the voltage controlled oscillator 15 via the DA converter 23.

Therefore, in the switching signal generating device having the configuration shown in the figure, an output DC voltage is obtained from the rectifier circuit 20 each time the mixed interference wave in the form of frequency-converted angle modulation passes through the bandpass filter 17, and the output DC voltage is The value allows the frequency of the interference waves to be identified and the number of interfering waves to be determined.

(Effects) As is clear from the above description, according to the present invention, in the double sideband transmission band of the vestigial sideband modulation type television broadcast wave, regardless of whether it is an upper sideband or a lower sideband, Multiple interfering interference waves can be canceled out at the same time, and since such interference waves are canceled out and removed at the intermediate frequency stage of the receiving device, it is possible to cancel out and remove the interference waves at the same time. An interference wave removal function can be easily added to a television broadcast wave receiving device, and the interference wave removal function can be achieved by a slight modification of the circuit configuration using conventional components. It should be noted that, of course, in cases where such simplicity of the circuit configuration is not the objective, or in special cases, the same high frequency as the television broadcast waves may be used.

In addition, since the quadrature phase synchronized detection output in the double-sided transmission band, which does not include the video signal component, is used to detect mixed interference waves, only the mixed interference waves can be canceled out and removed without damaging the video signal component. Good received image quality can be obtained.

Therefore, according to the present invention, regardless of whether the mixed interference wave is modulated or not modulated, regardless of the modulation format, and not limited to television broadcast waves using the vestigial sideband modulation method. It is said that it is possible to sufficiently eliminate all interference waves mixed asymmetrically with respect to the carrier wave into a modulated wave having double-sideband transmission components, regardless of the number of interference waves mixed in, the frequency distribution, or whether or not there is a change in the interference waves. A special effect can be obtained.

[Brief explanation of drawings]

Figures 1a, b, and c are characteristic curve diagrams showing the sideband distribution characteristics, in-phase component distribution characteristics, and quadrature component distribution characteristics of a television broadcast wave using the vestigial sideband modulation method, respectively, and Figure 2 is a characteristic curve diagram showing the present invention interference. FIG. 3 is a block diagram showing an example of the configuration of a wave cancellation receiving device; FIG. 3 is a block diagram showing another example of the configuration of the receiving device;
FIG. 4 is a spectrum distribution diagram showing an example of circuit operation in the same configuration example, and FIG. 5 is a block diagram showing a configuration example of the on-off switch switching signal generating device in the same configuration example. 1... Carrier wave regeneration circuit, 2... π/2 phase shift delay circuit, 8, 5, 16... Multiplier, 4... Low pass filter, 6... Phase compensation circuit, 7, 8, 13-1
~13-n, 17...Band pass filter, 9...
...Level adjustment circuit, 10...Delay circuit, 11...
Subtraction circuit, 12... Switcher, 15... Voltage controlled oscillator, 18... Limiter, 19... FM detection circuit, 20... Rectifier circuit, 21... A-D converter, 22... Arithmetic processing unit (CPU ), 23...D
-A converter, SW ₁ ~ SW _o ... Open/close switch.

Claims (1)

[Scope of Claims] 1. A carrier wave reproducing means for regenerating a carrier wave component from a carrier signal component of a modulated wave having both sideband transmission components received including an interference wave, and a carrier wave component regenerated by the means at π/2. A carrier phase shifting means for shifting the phase, and synchronization for synchronously detecting the carrier signal component of the received modulated wave in the double-side band transmission band using the recovered carrier component whose phase is shifted by π/2 by the means to extract a quadrature phase component. a detection means, a modulation means for modulating the regenerated and π/2 phase-shifted carrier wave component by the quadrature phase component, and a modulation means for modulating the carrier wave component phase-shifted by regenerating π/2 by the quadrature phase component; at least one that extracts the same frequency component as the wave
and subtraction means for subtracting the extracted same frequency component from the carrier signal component of the received modulated wave to cancel out and remove the interference wave mixed into the double sideband transmission component. An interference wave removal receiving device characterized by: 2. The receiving device according to claim 1, comprising a plurality of said wave means each having a different wave band, and selectively canceling out a plurality of said interference waves included in a carrier signal component of said modulated wave. 1. A receiving device for eliminating interference waves, characterized in that the interference waves can be removed. 3. In the receiving device according to claim 1 or 2, oscillation means with a variable oscillation frequency;
a frequency conversion means for sequentially converting the frequency of the carrier signal component of the received modulated wave by the output of the oscillation means; narrowband wave means for extracting a signal component of a predetermined narrow band from the output of the frequency conversion means; 1. An interference wave removal receiving apparatus, comprising: angle demodulation means for angle demodulating a component of a predetermined narrow band, and identifying the interference wave from a carrier signal component of the received modulated wave.